Final answer:
Block C in the agar jelly lab, which acted as a control by being kept in the dark, is crucial for interpreting the effects of light treatment on seed germination.
Step-by-step explanation:
In the agar jelly lab, the result of block C, which served as the control and was maintained in the dark, likely showed a different percentage of germination compared to blocks A and B.
We can infer that any differences in germination between the three blocks are attributable to the effects of light treatment, with block C representing the baseline germination in the absence of light stimuli.
Block A's exposure to red light and block B's exposure to red light followed by far-red light would reveal the specific influencing factors and the potential reversibility of red light's effects by far-red light on seed germination.
The conclusion from this experiment would provide insights into the role of light and, possibly, phytochrome activity in seed germination.